1. Field of the Invention
The present invention relates to the field of restorative dentistry in humans. Specifically, the present invention relates to a population of cells that can differentiate into dentin/pulp and a method of regenerating dentin/pulp.
2. Background Art
During tooth formation, interactions between epithelial and dental papilla cells promote tooth morphogenesis by stimulating a subpopulation of mesenchymal cells to differentiate into odontoblasts, which in turn form primary dentin. Morphologically, odontoblasts are columnar, polarized cells with eccentric nuclei and long cellular processes aligned at the outer edges of dentin (1). Following tooth eruption, secondary dentin is formed by odontoblasts in response to general mechanical erosion or disruption, and through dentinal degradation caused by bacteria (2). These odontoblasts are thought to arise from the proliferation and differentiation of a precursor population, residing somewhere within the pulp tissue (3). Despite extensive knowledge of tooth development, and of the various specialized tooth-associated cell types, little is known about the characteristics and properties of their respective precursor cell populations in the post-natal organism.
Dentinal repair in the post-natal organism occurs through the activity of specialized cells, odontoblasts, that are thought to be maintained by an as yet undefined precursor population associated with pulp tissue (1). To date, the identification and isolation of an odontogenic progenitor population from adult dental pulp tissue has never been performed. It is known that in certain conditions, cultures of pulp cells derived from early developing dental root tissue and pulp tissue can develop an odontoblast-like appearance with the capacity to form mineralized nodules in vitro (4) a trait normally attributed to cultures of bone or bone marrow cells (5, 6). More is known about the characteristics of multipotent bone marrow stromal cells (BMSCs) and their potential to develop into osteoblasts, chondrocytes, adipocytes, myelosupportive fibrous-stroma, and perhaps even muscle and neural tissues (7–12). They are characterized by their high proliferative capacity ex vivo, while maintaining their ability to differentiate into multiple stromal cell lineages.
Because the prior art does not provide for regenerating dentin/pulp tissue or producing a human tooth for restorative purposes, there exists a great need to find a means for producing tissue that can differentiate into a functional tooth. In this study, a clonogenic, rapidly proliferative population of cells from adult human dental pulp was isolated. These dental pulp stem cells (DPSCs) were then compared to human bone marrow stromal cells (BMSCs), known precursors of osteoblasts. Although they share a similar immunophenotype in vitro, functional studies showed that DPSCs produced only sporadic, but densely calcified nodules, and did not form adipocytes, whereas BMSCs routinely calcified throughout the adherent cell layer with clusters of lipid-laden adipocytes. When DPSCs were transplanted into immunocompromised mice, they generated a dentin-like structure lined with human odontoblast-like cells that surrounded a pulp-like interstitial tissue. In contrast, BMSCs formed lamellar bone containing osteocytes and surface lining osteoblasts, surrounding a fibrous vascular tissue with active hematopoiesis and adipocytes. This study is the first to isolate post-natal human dental pulp stem cells that have the ability to form a dentin/pulp complex.
The present invention overcomes the previous limitations and shortcomings in the art by providing a human adult dental pulp stem cell (DPSC) that can differentiate into dentin/pulp tissue and a method for regenerating dentin/pulp and for producing a human tooth.